Tag Archives: food colour

The kids don’t really like to eat celery (though I do), but they weren’t averse to using it for an experiment. What happens when we place celery tops into cups of coloured water?

At the start.

We chose five food colours, red, pink, green, yellow and blue. We placed some of each colour into five separate plastic cups and then filled the cups up to about half way with water. Each cup got its own celery top. I asked the kids what they thought would happen if we left them like that, they both thought the celery would suck up the water. We also talked about what would happen to the colours, and would we see a difference between the colours. I was predicting that blue and red would produce the most dramatic change, and L predicted that yellow and green wouldn’t do anything.

We left the celery for about an hour. By this time, we could see some colour rising up the stalks, and travelling through the leaves. The pink and blue ones had the most obvious change in colour.

Pink, blue and red (l-r) after an hour.

After an hour.

After about 24 hours, much more of the colour had been transferred from the cups into the leaves, producing a mottled effect on the leaves. We could also see the colour in the stalks. The red, pink and blue showed a major change in the colour, while the yellow and green ones were much harder to see. Looking closely at the green one, we could see the colour where some of the leaves were a little damaged, and around the edges of the leaves. The yellow one’s leaves appeared somewhat brighter than before the experiment, and we could see the yellow around the top of the stalk, but compared to the other colours, it was very difficult to see what had happened.

After 24 hours, the red, blue and pink (l-r) had a dramatic change.

This little experiment demonstrates the way plants suck up water throughout their stem and leaf systems. It is another example of capillary action at work. L was quite interested in it, but A mostly just liked the pretty colours the celery had turned 🙂